1. Field of the Invention
This invention relates to a support runner for use in suspended ceilings and the ceiling system made possible by use of the runner.
2. Description of the Prior Art
Suspended ceiling systems using inverted-T cross runners to support ceiling tile and the like are a common type of construction for office buildings and the like. In one type of design, the bottom portion of the inverted-T runner fits into kerfed areas in the ceiling tile and the ceiling tile present a continuous surface without exposure of the runner anywhere in the ceiling. In recent years, however, it has become desirable for appearance and design purposes to have an exposed runner to provide a highly decorative surface which interrupts the ceiling tile. Examples of various design of inverted-T runners having such a decorative surface are found in U.S. Pat. No. 2,767,440; U.S. Pat. No. 3,577,904; U.S. Pat. No. 3,757,668 and U.S. Pat. No. 3,207,057. Examples of modified runners to provide a highly decorative effect using a modification of the inverted-T runner include such designs as are disclosed in U.S. Pat. Nos. 3,596,425; 3,390,624; 3,440,789; and 3,301,165. Still other designs having a grooved decorative ceiling surface are shown in U.S. Pat. No. Des. 223,235 and U.S. Pat. No. 3,916,773. In each of these systems, the inverted-T runners are rigidly locked together to provide a rigid support for the ceiling system. A ceiling system provided by use of such supports has one serious deficiency. When the system is exposed to extreme heat, the T-runners expand and deform, and the ceiling tile fall from the T-runners as a result of this deformation.
Ceiling systems which overcome the problem of collapse upon exposure to heat have been almost nonexistent. One attempt to provide a fire guard in such systems is disclosed in U.S. Pat. No. 3,062,298, but this disclosure expressly provides for collapse of the ceiling to enable sprinkler devices to eliminate the fire. The only other known type of system is that which uses "knockout" portions in the runners and tees to accommodate expansion by controlled buckling, but the buckling then causes problems in retaining the ceiling tiles in place. It would be much more desirable to have the ceiling remain in place, and, if the ceiling is a fire-rated material, enable the ceiling to act as a fire barrier to prevent the fire from spreading to the supporting structure. To date, no known system has been provided for utilizing the decorative exposed flange with an inverted-T runner with construction sufficient to support the ceiling upon exposure to heat. The new and novel runners and ceiling systems provided in this invention make possible, for the first time, a ceiling system which overcomes all of the deficiencies of the prior known systems.